In recent years, the importance of handling a living body, such as a cell, an embryo, or an individual organism, to examine the function thereof and to allow a certain kind of chemical agent or physiological active agent to react with the living body to observe the function and morphological change of the living body has grown.
For example, as a sensitive, simple method of examining the effects of a chemical agent and a pharmaceutical commonly used in daily life on a living body, various tests have been attempted, such as exposing or introducing the chemical agent to cultured cells, embryos, or an individual organism, including an adult. Those tests are particularly useful for diagnosing diseases and in the field of drug development.
In the pharmaceutical field, examination of the main effect or the adverse effect of a chemical agent is essential for placing pharmaceuticals on the market. Examples of such effects on a living body include a carcinogenic/carcinostatic effect, a teratogenic effect, and an endocrine-disrupting effect.
Thus, there has been a demand for a system, which can be used to rapidly treat a large number of living bodies and to accurately evaluate the effects of the chemical agent and the physiological active agent on the living bodies by a bioassay. Also, in order to evaluate those living bodies in more detail, it is important to rapidly select and sort the living bodies.
However, in order for a large number of the living bodies to be rapidly treated using the above-mentioned system, the following predetermined operation must be effectively performed: arrangement of minute living bodies, such as embryos, at determined positions; addition of a predetermined agent to the living bodies; and measurement and sorting. In particular, an embryo must be treated in an extremely short period of time in the developmental process due to its rapid growth. However, there has not been developed a system in which the following operations are performed rapidly and practically on a large scale: arrangement of minute organisms; controlled administration of an agent, such as a chemical agent; analysis and evaluation of the living bodies with a bioassay system; and sorting of the living bodies. This results in a big obstacle to the research and development in the field.
As a method of arranging a minute living body, there is known a method in which a living body, such as a cell, is placed in a recess of a microwell plate by manipulation of a pipette or the like to isolate and arrange the living body individually. In general, because living bodies, such as cells or embryos, are very small and easily damaged, careful and accurate handling is required. For example, handling of an embryo of a biological organism requires the use of a micromanipulator. While a micropipette is manipulated or microscopic observation is performed, the position of the embryo is arranged and adjusted with optical tweezers using laser light. This operation requires skill, making it difficult to rapidly arrange and treat a large amount of embryos.
As an attempt to rapidly arrange the living bodies, Japanese Patent Application Laid-Open No. H10-165166 discloses the following method: supplying an embryo-suspending fluid to a plate for fixing cells in which a plurality of recesses, each having a shape matching a fertilized embryo, are formed on a porous plate; sucking the fluid from the back side of the plate; and arranging and fixing fertilized embryos.
In addition, Japanese Patent Application Laid-Open No. 2007-504816 discloses a device for and a method of handling cells, embryos, or oocytes.
The description of the method refers only to the method of arranging living bodies with a pipette.
Japanese Patent Application Laid-Open No. 2002-500373 discloses a method of analyzing a suspension of cells or the like while the suspension is held in a through-hole having a capillary form and a device for the method. Further, U.S. Pat. No. 6,027,873 also discloses a method of performing high-throughput screening of a suspension of cells or the like while the suspension is held in a through-hole having a capillary form.
However, while the arrangement method disclosed in Japanese Patent Application Laid-Open No. H10-165166 can be used to rapidly treat the living bodies, it has the following disadvantages: the plate for fixing cells must be a porous plate in which each recess matches the shape of a cell; and cells, such as fertilized embryos, may be damaged because the fluid is suctioned from the back side of the plate and the cells are pressed against the bottom of the plate. In addition, it is difficult to arrange a large number of living bodies using a pipette as disclosed in Japanese Patent Application Laid-Open No. 2007-504816. Besides, the methods disclosed in Japanese Patent Application Laid-Open No. 2002-500373 and U.S. Pat. No. 6,027,873 cannot arrange only one organism, such as an embryo, efficiently and cannot particularly select a specific organism for sorting and transfer purposes.